An example of a plug device having a plug or a jack device having a jack includes a charged device described in PTL 1, a data holding device, or a charging adapter.
The charged device described in PTL 1 is a plug device having a plug, and the data holding device and the charging adapter are jack devices having a jack.
A data line for transferring data is connected to the plug of the charged device. When the plug of the charged device is connected to the jack of the data holding device, the charged device acquires data from the data holding device via the data line.
Further, the charging adapter has a mechanical detection switch, and when a connection of the plug of the charged device to the jack of the charging adapter is mechanically detected by the detection switch, a built-in battery built into the charged device is charged using the data line, in the charged device.